"As a matter of public policy, hospitals and emergency physicians are required to treat any patient who walks through the door, regardless of ability to pay. In turn, health maintenance organizations are obligated to reimburse the providers for an enrollee's care. HMOs frequently contract with independent practice associations, delegating, among other duties, their reimbursement responsibilities. This arrangement has worked out well for the HMOs, who always get their premium payments from patients, with relative immunity. However, it has not always worked out so well for the providers (hospitals, trauma surgeons and emergency physicians), especially when the IPAs experience serious financial trouble that renders them unable to pay."